fx:Synchronize markup extension, #{x}

The fx:Synchronize markup extension establishes a bidirectional binding. It is only valid in property-consumer position and cannot be used where a value or ObservableValue is expected.

fx:Synchronize establishes a bidirectional binding between the target and source Property.

A leading .. in the source path selects the content of the target and source collection. In that form, fx:Synchronize establishes a bidirectional content binding between the source and target collections.

Its prefix notation is #{x}, where x is the source path.

Properties

Property	Description
path	A string that specifies the source path. This is the default property.
format	The path to a java.text.Format instance passed to StringProperty.bindBidirectional(Property<?>, Format). The format path is evaluated once when the synchronization is set up. This property is only applicable to StringProperty targets.
converter	The path to a javafx.util.StringConverter instance passed to StringProperty.bindBidirectional(Property<T>, StringConverter<T>). The converter path is evaluated once when the synchronization is set up. This property is only applicable to StringProperty targets.
inverseMethod	The path to an inverse method for the method referenced in path. This can also be the name of a constructor.

Usage

<!-- Element notation -->
<object>
    <property>
        <fx:Synchronize path="myPath"/>
    </property>
</object>

<!-- Attribute notation -->
<object property="{fx:Synchronize path=myPath}"/>

<!-- Attribute notation with omitted "path" -->
<object property="{fx:Synchronize myPath}"/>

<!-- Prefix notation -->
<object property="#{myPath}"/>

<!-- Bidirectional binding with javafx.util.StringConverter -->
<object property="#{myPath; converter=myConverterPath}"/>

<!-- Bidirectional binding with java.text.Format -->
<object property="#{myPath; format=myFormatPath}"/>

Inverse method in a bidirectional method binding

The @InverseMethod annotation is available in the markup runtime library.

If a fx:Synchronize expression converts the source property with a method call, the compiler needs a way to translate changes on the target property back to the source property.

For a method m(B)→A, the inverse method must have the corresponding shape n(A)→B. In other words, both methods must accept exactly one argument, and the parameter and return types must be reversed.

The inverse method can be supplied explicitly with the inverseMethod parameter:

<TextField text="#{stringToDouble(stringProp); inverseMethod=doubleToString}"/>

When the method declaration is annotated with @InverseMethod, the inverse method can be inferred automatically and does not need to be repeated in markup:

@InverseMethod("stringToDouble")
public String doubleToString(double value) {
    return Double.toString(value);
}

@InverseMethod("doubleToString")
public double stringToDouble(String value) {
    return value != null ? Double.parseDouble(value) : 0;
}

<TextField text="#{doubleToString(doubleProp)}"/>

The InverseMethod annotation names another method on the same class. It is legal for a method to name itself as its own inverse when its parameter type and return type are the same.

An explicit inverseMethod=... in markup is still useful when the annotation is not present or when a different inverse should be chosen than the one declared on the method.